Thermally Stimulated Discharge Currents in Tubular Magnetoelectrets of Polymethyl Methacrylate

Abstract

Thermally stimulated discharge currents (TSDC) have been obtained from Perspex tubular magnetoelectrets(M.E.) using different linear heating rates (1.0°, 1.5°, 2.0°, 2.5° and 3.0°C/min), for samples prepared at various polarizing fields (Hf) and forming temperatures (Tf), in M.E. containers made of ferro–as well as diamagnetic materials. TSDC spectra consist of three peaks with temperature maxima of 54^°±3°C, 134^°±3°C and 148^°±3°C which are termed as β, α and ρ peaks respectively. The values of activation energy and pre-exponential factor of relaxation time have been calculated for α peak which is quite isolated from β and ρ peaks and are found to be 0.68 eV and 6.55×10-15 seconds respectively. The variation of relaxation time and peak current with Tf indicates that far too many dipoles must be aligned to produce the observed effect. TSDC using different heating rates shows that low heating rates are preferable. Ferromagnetic material (cast iron) seems to be more suitable than diamagnetic (brass) for the preparation of tubular M.Es.